1. Field of the Invention
This invention relates to the field of disk drives. More particularly, this invention relates to the field of a pitch moment-balanced gimbal for improved shock resistance in disk drives such as magnetic hard disk drives.
2. Description of Related Art
A disk drive typically has a disk or platter of spinning disks over which read/write heads are suspended. Disk drives include both magnetic hard disk drives and optical disk drives. The present invention is applicable to disk drives generally. In a magnetic hard disk drive, a read/write head is suspended by a disk drive suspension, which is an arm-like structure which extends from an area off the disk to an area over the disk. Such suspensions commonly include a load beam, which forms the suspension's structural backbone, and a stainless steel gimbal, which allows the read/write head to slightly pitch and yaw over imperfections in the disk.
The read/write head is an electronic circuit, typically with a magnetic pickup transducer, which is formed on a slider. The slider is sometimes referred to as the “head.” The slider has an aerodynamically shaped surface which produces a turbulent air bearing between it and the disk surface when the disk is rapidly spinning, sometimes approaching 15,000 rpm. The air bearing allows the slider to fly extremely closely over the disk surface without touching.
FIG. 1 is side elevation view of a simplified prior art suspension 10 and magnetic disk 50. Suspension 10 typically includes a base plate secured by a swage hub 12 to a load beam 14. Load beam 14 has a dimple 16 formed in it to support gimbal 30. Gimbal 30 has a leading edge 31 and a trailing edge 32. A slider 34 which contains the magnetic read/write head is affixed to gimbal 30. Dimple 16 provides a pivot point about which gimbal 30 and slider 34 affixed thereto can pitch and roll freely so that slider 34 can follow disk surface 52 as disk 50 flutters due to environmental shocks, imperfections in the flatness of surface 52, imperfections in the bearings upon which disk 30 turns, and other static and dynamic anomalies. Slider 34 “flies” over surface 52 of disk 50 on a cushion of air created by the air flow caused by the spinning of disk 50. This cushion of air is called an “air bearing.”
The disk drive suspension 10 is designed with a cantilever spring within load beam 14 so that the spring forces slider head 34 toward the disk. The spring is flexible enough so that its “gram force” exactly opposes that of the air bearing, yet rigid enough to resist external shocks. Such shocks may be caused by a user dropping the disk drive. Shocks which occur while slider 34 is suspended over the spinning disk are called operational shock events, or “op-shock” events for shorthand.
During operational shock events, slider 34 tends to separate from the rotating disk surface 52 beyond the normal air bearing separation distance. An operational shock can therefore cause momentary failure in the reading or writing of data. In a worse case scenario, an operational shock can cause the slider to crash onto the surface of the disk causing complete failure of the disk drive.